Hi Yu,
The videos where made in version 12 while the trail versions are version 13 so it is normal to see quite some inconsistencies as Odoo keeps evolving. The e-learning team creates quite some new content though (they have about 64 new videos planned) so you might see an updated version come up in the future. To me the real problem is that they do not segment/mention the versions so that you can easily find the right ones.
As for the exam: the e-learning isn't specifically built to train you for the functional exam. It is built to help people understand concepts in Odoo. If you just follow these e-learning videos it won't be a guarantee for you to pass the exam or in fact a guarantee that the questions come up in the exam too. See them as two different components in the Odoo eco-system. I know the e-learning team is trying to bring them closer together in the future though.
The main topics you should know well functionally are accounting, purchase, sales, website, CRM and project. Those have the most questions on the exams and are the most difficult questions. You'll find various tutorials and guides online about Odoo concepts but at the moment there is no real go-to place that has it all. :)
Best of luck,
Yenthe
Trial version might be v13 and the videos are of v12
@Niyas so does the video covers everything that will be on the exam?